It is well known in the art to provide bobbins onto which there are wound filaments to be paid out from the bobbin at a later time. One particularly interesting example of filament is the optical fiber. Optical fibers are used as communication links between moving objects and control stations, because it is possible to wind a very long fiber, of the order of kilometers, on a relatively small bobbin, and to transmit data along the fiber at a high rate. Optical fiber canisters of this type, including an optical fiber wound on a bobbin, are used in a variety of applications, e.g., for communication purposes. Throughout this specification reference will be therefore made to optical fibers, it being understood that the same applies, mutatis mutandis, to other filaments as well.
Bobbins adapted to be used as a base for optical fiber canisters can be made in a variety of ways and from different materials. For instance, they may be of aluminum, or can be made of composite material, such as described in U.S. Pat. No. 4,995,698. However, all prior art manufacturing processes suffer from substantial drawbacks. In the case of aluminum bobbins, for instance, it is necessary to work the surface of the bobbin in order to produce the threaded grooved surface which is commonly required in order to lay the first layer of optical fiber. Alternatively, the surface may be prepared for this purpose by other methods, e.g., by winding first a base wire which creates the grooved surface.
In the case of a composite bobbin such as that made according to the aforesaid U.S. patent, surface finishing is also needed, in order to smooth out inequalities of the surface which may have greatly undesirable effect on the winding of the optical fiber, and to provide the required grooved surface. Additionally, the bobbin normally is made by stages, the first one being manufacturing the main body which is frusto-conical in shape. However, additional elements must be provided, e.g., for fastening the bobbin onto the body from which the optical fiber is paid out. This is normally achieved by providing anchoring means, e.g., a ring, connected to the larger diameter of the bobbin. This of course requires an additional operation, unless the bobbin is made of cast material, e.g., aluminium, in which case it is possible to create the desired anchoring means integrally with the body of the bobbin.
As a result of the aforesaid problems, production of bobbins of this type requires a number of steps, and the surface of the bobbin may suffer from irregularities due to machining thereof.
Another drawback of prior art methods is that they are relatively limited in the choice of construction materials and in the tailoring of the properties required of the bobbin, as will be more fully explained hereinafter.
It is an object of the present invention to provide a method for manufacturing bobbins of this type, which is free from the aforesaid drawbacks of prior art methods.
It is another object of the invention to provide a method by means of which a bobbin can be produced in an automated process providing a product of constant high quality.
It is still further object of the invention to provide a production method which is flexible as far as the construction materials and the properties of the bobbin are concerned. Other objects of the invention will become apparent as the description proceeds.